One huge factor that this study apparently left out is that more prestigious universities can generally offer much better financial aid, and hence offer a much

One huge factor that this study apparently left out is that more prestigious universities can generally offer much better financial aid, and hence offer a much better ROI for middle and low income students. MIT and Podunk U might have the same effect on your salary, but if MIT is charging you only $5,000 a year (including room & board), it's going to be an order of magnitude better ROI.